[NTLUG:Discuss] SCSI problems - (Was: aic7xxx: infinite...)

[Steve Baker]

Kevin Brannen wrote:

> SCSI problems are generally attributible to 3 things:
> 1. ID settings.
> 2. Termination.
> 3. Cables.
> 
> Make sure all SCSI devices on that controller are different, not set
> to 7, and that the controler is set to 7.  If an internal chain,
> triple check that only the last device (tape?) on the cable is
> terminated, and that none of the others are.  If external, make sure
> none of the devices are terminated, as there will be a terminator
> "plug" on the back of the external case.  Lastly, bad cables are
> sometimes a problem.

Hmmm - this is an appropriate time (for me) to discuss SCSI.

I've been wrestling with a new CD-writer.

I have been using an adaptec AHA152x to drive my scanner for over
a year now - with no problems.  I was given the chance to buy a
completely unused (if a little old) HP6020 CD writer (it's the
same device as the Philips 2600) - since I had a spare port on
the SCSI card, I jumped at the chance.

OK so with very little hassle, I got my SuSE 6.4 box to READ the
CD drive - I can mount the CD-ROM, read files - all without errors.

However, when I use the 'cdrecord' program - or anything that does
raw accesses to the drive (other than to read it's ID) - my computer
completely locks up.  I can't even telnet into it or Ctrl-ALT-DEL.

I tried unplugging the scanner - no change.

The cdrecord command to check the CD-writer's type works OK and
reports exactly the right model number - it even sees the
scanner if I leave that plugged in.

It's not just that writing to the drive fails.  There is a Linux
command to read an audio CD into a WAV file - that too locks up
the kernel.

I emailed the author of the CD-writer-HOWTO and he suggested
interrupt problems - but I'm as sure as I can be that INT-9
is free of everything except the CD-writer.

>From the list of suggestions for typical sources of SCSI
problems:

ID SETTINGS:

  It's ID is 4 - the scanner *was* 6 - but that's disconnected
  now "just to be sure".

TERMINATION:

  I wasn't quite sure what was the right thing to do.  The
  Adaptec card has an internal ribbon connector (which
  is what the CD-writer is plugged into) and an external
  connector (which is what I was using for the scanner).
  Right now, both the scanner (when plugged in) *and* the
  CD-writer have termination - which I imagine is the right
  thing - and since the scanner still works OK - and
  the CD-writer works for reading - I can't believe it's that.
  In case it was intermittant, I read an entire CD onto my
  hard drive - then re-read the same CD with a normal CD-ROM
  drive on my son's computer and diff'ed the two - no errors.

CABLES:

  Well, the CD-writer has a vanilla grey ribbon cable -
  about a foot long...what could be wrong with that?
  The scanner cable is a shielded bundle about 3 feet
  long - and came with the scanner. This could be
  problematic I suppose - but it's disconnected right now.

> I really like SCSI devices, they generally aren't that hard to get
> working most of the time.

Grrrrrrr  :-(

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjbaker1 at airmail.net (home)  http://www.woodsoup.org/~sbaker
sjbaker at hti.com      (work)